The present invention relates to the field of food extrusion, and more particularly deals with a process for improving the manner in which fat can be added to an extrusion-expanded food product.
Fat is an important dietary component and can also provide taste and textural variations to food products depending upon the type and/or the manner of addition. It has about twice the caloric density of protein and carbohydrates and is therefore a good source of calories. Many fats are also very taste attractive as food additives.
Foods intended for physically active humans and animals will desirably have high caloric contents. One class of foods where a high caloric density is particularly important is that especially formulated to meet the nutritional requirements of puppies. Because fat is a concentrated source of calories and is well liked by puppies, it would be desirable to increase the caloric density of conventionally formulated dog foods by simply adding more fat. Unfortunately, the addition of fat to an extruder-expanded farinaceous pet food beyond a level of 6 or 8% is fraught with difficulties.
Typically, expanded dog foods are prapared from a farinaceous mixture containing starch, protein, fat, and preferably also flavors colors, fiber and vitamins and minerals. Sufficient water is added to the farinaceous mixture to increase the moisture content to from about 20 to 35%. The mixture is then subjected to heat and pressure and expanded from an extruder. Upon extrusion, some of the water is flashed off causing expansion and partial drying of the product. The extrudate is cut into kibs upon exiting the extruder. Additional drying in an oven further reduces the moisture content to around 8 to 10%.
Conventionally, the fat content of the dog food kibs produced in this manner is increased to the desired level by surface coating with a fat such as tallow. Unfortunately, the addition of levels of tallow of over about 6 to 8% in this manner causes serious problems of product clumping and packaging material staining. These problems can be controlled only with significant expenditures. Where it has been attempted to add the higher amounts of fat directly to the farinaceous mixture prior to extrusion, product expansion has been reduced to an undesirable extent such that the products become undesirably dense. Accordingly, there is a present need to develop an improved process for providing higher levels of added fat in extrusion-expanded pet foods.
Fat coatings and high fat contents can also be useful for a number of purposes in foods intended for human consumption, such as ready-to-eat dry breakfast cereals. For example, as with the puppy food described above, there is a need for high energy content breakfast foods for human consumption. Moreover, the use of fat coatings on cereals has, in various applications, been shown to provide increased stability to oxidation of the natural fat content of the cereal and has also been employed as a coating to reduce the rate of hydration of the cereals when employed in milk. The addition of added fat directly to the extruder in preparing products of this type has caused excessive extruder surging as well as decreased product expansion. Here again, there is a present need for providing an improved process for adding fat to an extrusion-expanded, ready-to-eat breakfast cereal.